1. Field of the Invention
The present invention relates to improvements in systems for removing cells from bone marrow.
2. Prior Art
Monoclonal antibodies bound to e.g., polystyrene microspheres containing magnetite, have been used to remove tumor and other types of cells from bone marrow destined for autologous transplantation. The small magnetic beads can be targeted to the surface of tumor cells to render them magnetic. See Treleaven et al, Lancet, Jan. 14, 1984, pp. 70-73. The flow system which uses permanent samarium cobalt magnets and an electromagnet effects the removal of the "magnetic" tumor cells from the bone marrow. The system is designed to be used with a wide variety of tumor cells, so that by changing panels of monoclonal antibody the system can be used for "cleaning" the bone marrow in many different malignancies.
Although the systems presently in use provide for relatively rapid and efficient removal of the cells, they are subject to several disadvantages. Thus, the general utility of the system is limited by the requirement for a large electromagnet with its associated power supply. Moreover, the system must be assembled only after sterilization of the components. The system is also subject to large variations in the efficiency of conjugated microsphere removal throughout the circuit. There is also no capability for varying the magnetic field strength along the flow path to ameliorate the difficulties associated with the above noted variations along the system. Finally, it is difficult to obtain positive retention of the microspheres on the smooth interior surfaces of the removal chamber.
It is an object of the present invention to provide an improved method and apparatus for the removal of conjugated, magnetic cells from bone marrow which do not suffer from the above noted disadvantages.